1. Field of the Invention
The present invention relates to a color photographic light-sensitive material having improved color reproducibility and, more particularly, it is concerned with a color photographic light-sensitive material whose color image quality is improved by applying a compound which selectively shows a color correcting effect between layers.
2. Description of the Prior Art
Color photographic light-sensitive materials can be roughly classified into two groups: (1) color photographic light-sensitive materials which do not contain couplers (non-incorporated coupler system) wherein a developer containing a diffusible coupler is used; and (2) color photographic light-sensitive materials which contain couplers (incorporated coupler system) wherein non-diffusible couplers are incorporated independently in each of the light-sensitive layers of a light-sensitive material so as to maintain the independent function of each layer.
The latter system usually comprises a blue-sensitive emulsion layer (BL) which contains a yellow coupler and which is mainly sensitive to blue light (substantially to wavelengths less than about 500 nm), a green-sensitive emulsion layer (GL) which contains a magenta coupler and which is mainly sensitive to green light (substantially to wavelengths of about 500 - 600 nm), and a red-sensitive emulsion layer (RL) which contains a cyan coupler and which is mainly sensitive to red light (substantially to wavelengths longer than about 590 nm). These BL, GL and RL must perform their own independent functions. For this reason, the latter system further contains a so-called intermediate layer (ML), a filter layer (FL) for filtering out light including ultraviolet light, an anti-halation layer (AHL) and a protective layer (PL), thus forming a multi-layered stratal structure of two or more layers.
With the multi-layered incorporated-coupler color photographic light-sensitive materials, it is necessary that at least the BL, GL and RL should independently perform their functions in a fresh condition, upon storage of the unexposed material or upon imagewise exposure and in the step of development-processing, so as to obtain excellent color reproducibility. In addition, it is necessary that the BL, GL and RL should independently possess appropriate spectral sensitization distributions in appropriate wave-length regions and contain couplers capable of providing color images having appropriate spectral absorptions. However, color photographic light-sensitive materials which have so far been developed possess numerous defects.
A first defect thereof in connection with color reproduction lies in the spectral adsorption characteristics of the colored images obtained from the couplers used. That is, sufficient light adsorption is not attained in a specific wave-length region and, in addition, the light absorption extends too widely to other wave-length regions, e.g., undesirably into shorter or longer wave-length regions. Of the yellow couplers, magenta couplers and cyan couplers, this defect is particularly conspicuous with magenta couplers. This defect results in a narrow color reproduction region of the color image, distortion of the color hue and, particularly, a reduction in saturation.
A second defect lies in that, during the step of development processing, the image development of a specific light-sensitive emulsion layer can cause coloration of the coupler contained in a neighboring light-sensitive emulsion layer. For example, in some cases, image development of the GL can induce coloration of a cyan coupler contained in the RL. These defects result from the diffusion of the oxidation products of the color developing agent, which are produced by the development of a specific light-sensitive layer, into a neighboring light-sensitive layer, color formation at the layer into which the oxidation products have diffused, and from the induction of chemical or physical development in the neighboring layer upon development of a specific light-sensitive layer.
A third defect lies in that a sensitizing dye used diffuses from a specific light-sensitive emulsion layer into an adjacent light-sensitive emulsion layer to sensitize the adjacent layer and provide an unsuitable spectral sensitization distribution.
The above-described defects will cause the so-called "color mixing" because the color image-forming reaction in a specific light-sensitive emulsion layer disadvantageously affects the neighboring light-sensitive emulsion layers which should be independent of the other layers and induces color image formation, which image overlaps the color image of the specific light-sensitive emulsion layer.
One known method to remove the above-described defects is a method of reducing "color mixing" itself by, e.g., providing an ML and an FL or incorporating in an ML a reducing compound such as a hydroquinone derivative or a phenol derivative, a scavenger for the oxidation product of a color developing agent, a colorless compound capable of coupling with it, a color coupler capable of forming a diffusible dye, a diffusion-inhibiting agent for a sensitizing dye or a coupler, such as fine silver halide grains colloidal silica, an anionic, amphoteric, nonionic or cationic surface active agent, a cationic hydrophilic synthetic polymer, polymer latex and the like. However, these methods are not satisfactory.
Another method for removing "color mixing" lies in the introduction of an element which is positively provided with a "color correcting" function. One such method involves using a colored coupler provided with an auto-masking function. Related methods are described in U.S. Pat. Nos. 2,449,966; 2,455,170; 2,600,788; 2,428,054; 3,148,062; and 2,983,608 and British Pat. No. 1,044,778. However, with this method, the unexposed area is also strongly colored. Therefore, this method cannot be applied to positive color light-sensitive materials. This is attributed to the fact that, in the color development-processing step employed, the product formed as a result of the elimination of the eliminatable azoaryl group tends to cause fog, which deteriorates the graininess or granularity of the color image formed.
Another method involves using a so-called "DIR coupler." DIR couplers are those couplers described by C. R. Barr, J. R. Thirtle and P. W. Vittum, Photographic Science and Eng., vol. 13, pp. 74-80 (1969) and ibid, pp. 214-217 (1969), or in U.S. Pat. No. 3,227,554. Usually, the use of a DIR coupler conspicuously brings about an intralayer (or intraimage) effect within a light-sensitive emulsion layer in which such is used by restraining the development therein, such as an improvement in graininess and an improvement in sharpness of color image by the edge effect in preference to the interimage (or interlayer) effect. It is generally known that a DIR coupler brings about an intraimage effect. However, since the DIR coupler which is disclosed in U.S. Pat. No. 3,227,554 causes a strong development-restraining effect upon color development at developing centers in proportion to imagewise exposure-image development, the use of a DIR coupler has the defect that gradation (gamma) is deteriorated or maximum color density (D.sub.max) is reduced. Therefore, in order to more effectively perform the function of "color correction" relating to the present invention, those couplers become necessary which exhibit an interimage effect rather than the effect of restraining development within a particular layer. In connection with a DIR coupler, the chemical structure of the compound which effectively exhibits the interimage effect rather than the intraimage effect cannot be determined by merely considering the chemical structures of the mother nucleus of known couplers or the chemical structures of the splitable groups thereof. Because, the effect of "color correction" due to a DIR coupler is obtained as a result of complicated factors, e.g., the independent or composite factors arising in the elimination-coupling reaction rate of DIR coupler, the development-restraining activity of the split group, the diffusibility thereof in a light-sensitive layer, the developing rate of each copresent light-sensitive emulsion itself, the coupling activity of the couplers copresent in the same layer or present in other layers, the mutual interaction with the compounds copresent in an ML or an FL, the spectral absorption characteristics of colored dye, and the like.
Thirdly, there is a method of using a substantially fogged emulsion or a direct positive emulsion, a method of using an internally fogged emulsion or an internal latent image emulsion, a method of employing the Luckey effect, or a like method. However, these methods of using silver halide photographic emulsions entail a reduction in sharpness due to exposure light-scattering effect of the grains therein, the difficulty in controlling the photographic properties of the emulsion, the photographic side effects, and the like.
Fourthly, there is a method of controlling the halide composition of silver halide emulsion itself which is used in each layer of the BL, GL and RL of the multi-layered structure, e.g., controlling the ratio of the content of iodide ion to bromide ion, controlling the distribution of a restraining element between the layers, and the like. However, the effect of "color correction" by controlling these factors is not satisfactory.
In addition, such factors as the developing agent content, the halide ion content the sulfite ion content, the hydrogen ion content and its buffering ability, the exhaustion degree thereof, and the like. However, the effect of "color correction" by controlling these factors is not satisfactory, either.
As the aforesaid DIR coupler, a 2-equivalent coupler having a 2-benzotriazolyl group is already known, for example, as described in U.S. Pat. No. 3,617,291. As set forth in this patent, this coupler has an excellent 2-equivalent property and has an excellent property of emitting fluorescence. Furthermore, this coupler provides an excellent fast colored image and possesses a development-restraining property. However, this strong fluorescence-emitting property is disadvantageous for the purposes of the present invention. For example, when used for a positive light-sensitive material, this coupler reduces the optical density of a color image formed in an adjacent layer, which is different from this coupler-containing layer and which has substantially a different hue, and the coupler shifts the hue, resulting in a deterioration of the deep shadow gradation of the image. On the other hand, when used in a negative light-sensitive material, this coupler fluoresces due to exposure to light upon printing, thus reducing the sharpness of the printed image. The effects described in the specification of the aforesaid patent appear only in the colorless white area of a positive light-sensitive material using, particularly, a reflective support or only when the coupler is used in a layer closest to the support. In addition, this coupler strongly exhibits an intralayer effect and, as compared with this, this coupler exhibits a small interlayer effect. In addition this patent specification does not describe the effect of "color correction" with which the present invention is concerned.
An object of the present invention is to remove the abovedescribed defects and to provide a color light-sensitive material having an enhanced effect of "color correction."
More particularly, a primary object of the present invention is to improve the color reproducibility by using the coupler of the present invention which reduces gradation (gamma) or maximum color density (D.sub.max) to a lesser extent and provides interlayer effect or interimage effect.
Another object of the present invention is to provide a novel 2-equivalent coupler.
A further object of the present invention is to provide a novel coupler which can be inexpensively produced on an industrial scale with a stable quality using a process different from that employed for synthesizing conventional DIR coupler.
Still a further object of the present invention is to provide a non-fluorescing coupler in contrast to that described in U.S. Pat. No. 3,617,291.
These and other object will become apparent from the detailed descriptions in the specification of the present invention.